1. Field of the Invention
The present invention relates to a novel method of producing a thin film electrically superconducting solid. Specifically, the method involves casting a thin film of unsaturated organic acid metal salts, covering selected portions using a pattern (mask), crosslinking the exposed portion using electromagnetic radiation, removing the unreacted materials, sintering the material remaining and annealing in oxygen to produce the patterned super-conducting solid metal oxides.
2. Description of Related Art
J. G. Bednorz and K. A. Miller (1986), Z. phys., Vol. B64, p. 189, first disclosed the high critical temperature (T.sub.c) electrical superconductor with onset T.sub.c at 30K in a Ba-La-Cu-O system. This report sparked a massive research in all phases of producing and examining superconducting mixed metal oxides. It is now reported that compounds of the Q-Ba-Cu-O system (where Q is yttrium or a rare-earth metal) exhibit superconductivity above liquid nitrogen temperature (77K). See M. K. Wu, et al. (1987), Physical Review Letters, Vol. 58, p. 908.
A number of general methods have been described to produce superconducting films of this system. These include, for example, sputtering (H. Adachi, et al. (1987) Japanese Journal of Applied Physics, Vol. 26, P. L709), plasma spraying (R. A. Neiser, et al. (1987), Materials Science and Engineering, Vol. 91, p. L13, screen printing (H. Koinuma, et al. (1987), Japanese Journal of Applied Physics, Vol. 26, p. L761), electron beam (EB) evaporation (R. B. Laibowitz, et al. (1987), Physical Review Letters, Vol. 58, #25, p. 2684-2686), and laser evaporation (D. Dijkkamp, et al. (1987), Applied Physics Letters, Vol. 51, p. 619).
In these methods, preparations from the vapor phase (except for screen printing) are expected to be available for fabricating high quality high resolution films suitable for electronic devices.
Art of general interest in this area includes the following:
H. Nasu, et al. (April 1988), Japanese Journal of Applied Physics, Vol. 27, #4, pp. L536-L537, which discloses the preparation of BiSrCaCu.sub.2 O.sub.x films having a T.sub.c greater than 77K by pyrolysis of saturated organic acids.
T. Maruyama, et al. (1988), Japanese Journal of Applied Physics, Vol. 27, #11, pp. L2084-L2087 discloses superconducting Bi-Sr-Ca-Cu-O thin films prepared by thermal decomposition of metallic complex salts.
K. Hoshino, et al. (1988), Japanese Journal of Applied Physics, Vol. 27, #7, pp. L1297-L1299 discloses the preparation of superconducting Bi-Sr-Ca-Cu-O screen printed thick films on magnesium oxide substrate and silver metal tape.
S. Makida, et al. (1988) Chemistry Letters (Chemical Society of Japan), pp. 2053-2054 disclose the preparation of high T.sub.c Bi-Sr-Ca-Cu-O films on metal substrates by pyrolysis of saturated 2-ethyl hexanoates.
D. W. Murphy, et al. (1988), Science, Vol. 241, p. 922-929 discloses a number of processing techniques for the high T.sub.c 93K superconducting material Ba.sub.2 YCu.sub.3 O.sub.7.
K. Terashima, et al. (1988) Applied Physics Letters, Vol. 52, #15, pp. 1274-1276 discloses the preparation of superconducting Y-Ba-Cu-O films by a reactive plasma evaporation method.
H. Nasu, et al. (1988), Nippon-Seramikkusu-Kyokai-Gakujutsu-Ronbunshi, Vol. 96, #6, pp. 710-713, discloses high T.sub.c superconducting Ba.sub.2 YCu.sub.3 O.sub.x films prepared by pyrolysis of saturated organic or inorganic acid salts.
H. Nasu, et al. (1987), Chemistry Letters (Chemical Society of Japan), pp. 2403-2404 which discloses superconducting Y-Ba-Cu-O films having a T.sub.c greater than 70K prepared by the thermal decomposition technique of Y-, Ba-, and Cu-2-ethylhexanoates.
H. Nasu, et al. (1988), Journal of Materials Science, Vol. 7, pp. 858-860, discloses Ba.sub.2 YCu.sub.3 O.sub.x films with a T.sub.c (end) greater than 80K prepared by the pyrolysis of saturated 2-ethylhexanoates.
J. Mannhart, et al. (1988), Applied Physics Letters, Vol. 52, #15, pp. 1271-1273 discloses a material for micro-patterning of high T.sub.c films with a excimer laser.
H. Shimojima, et al. (1989), Japanese Journal of Applied Physics, Vol. 28, #2, pp. L226-L228, discloses the preparation of high T.sub.c superconducting Bi-Pb-Sr-Ca-Cu-O film by pyrolysis of saturated organic acid salts.
E. J. A. Pope, et al., 1988 Annual Materials Research Society Fall Meeting, p. 214, briefly mentions the synthesis of organometallic methacrylate polymers, and their pyrolysis to form superconducting oxide coatings. This abstract does not describe experimental details or patterned superconducting films.
All references, patents, standards, etc. cited in this application are specifically incorporated by reference in their entirety.
None of the available art teaches or suggests the use of an unsaturated organic acid metal salt solution which is configured or cast as a film, then covering portions of the film with a pattern, irradiating the film to polymerize and crosslink the exposed portions, removing the unpolymerized portions, heating the remaining pattern of organic metal salts to about 900.degree. C., then producing the superconducting oxide followed by slow cooling and annealing. The present invention provides such a method to produce patterned superconducting thin film.